Catheters for manipulation of the esophagus are known in the art. For example, U.S. Pat. No. 7,621,908 to Miller, incorporated by reference herein, describes a catheter for manipulation of the esophagus that uses a control wire associated with a catheter tube, the control wire changing the shape of the catheter and displacing the esophagus relative to the heart to reduce the risk of an esophageal fistula resulting from atrial radio frequency (RF) ablation. In relevant part, this reference requires use of a pair of control wires and/or a control wire utilizing a curved portion to manipulate the catheter to move the esophagus.
As is described by Miller, the goal of the surgical treatment of atrial fibrillation is to block or interfere with impulses radiating from ectopic foci inside the pulmonary veins that triggered atrial fibrillation. Among the first intra-heart surgical treatments for atrial fibrillation was demonstrated by the Leipzig group in a procedure referred to as, endocardial linear lesion, to connect the pulmonary vein to the mitral annulus during open heart surgery.
The Mayo Clinic is known for another open heart surgical procedure, termed the Maze procedure, in which multiple cuts are created in the atrial muscle in a maze pattern. These cuts produce scar tissue that does not carry electrical impulses and, as a result, the stray impulses causing atrial fibrillation are eliminated, producing a normal coordinated heartbeat.
More recently, cardiology specialists, called electrophysiologists, have used cardiac catheters to ablate the heart tissue without the need for open heart surgery. In this procedure, an RF catheter is inserted into the atrium and a series of ablations or burns are performed around the mouth of the pulmonary vein and the left atrial wall. The ablations also form scar tissue, blocking stray electrical impulses to restore normal heartbeat. During RF catheter ablation, lesion depth, extension and volume are related to the design of the ablation electrode and the RF power delivered.
Among the complications that may arise is pulmonary vein stenosis if the ablations are too close to the mouth of the pulmonary vein. Another serious, and possibly fatal, complication is atrial-esophageal fistula caused by thermal penetration of the walls of the atrium and esophagus. The atrial-esophageal fistula can lead to pericarditis, or fluid between the outer wall of the heart and the pericardium, restricting the heartbeat, hemorrhage, or other life threatening conditions.
The atrial-esophageal fistula, or hole, in the esophageal wall may result, in part, from simple anatomy and the RF power needed to develop ablations, as well as the design of the catheter electrode tip and other contributing factors such as movement of the esophagus during the procedure.
The esophagus is located at the center of the posterior mediastinum and is separated from the atrium only by the pericardial sac and/or a thin layer of fatty tissue, and may be in contact with the atrium. The left atrium wall thickness is about 2-4 mm, and the esophagus 10 thickness is about 2-3 mm. The esophagus 10 is supported at its upper end near the trachea 21 and transits the diaphragm 22 to connect with the stomach. The esophagus 10 is supported at its lower end by the diaphragm 22. The thoracic portion 9 of the esophagus 10, between the trachea 21 and the diaphragm 22, is mobile and loosely restrained only by soft tissue. This allows the esophagus to move in response to swallowing food, cardiac and lung movement, as well as upper body movements. This flexibility of the esophagus complicates the problem of avoiding atrial-esophageal fistula.
Currently, several techniques are employed by the electrophysiologists to reduce the likelihood of an atrial-esophageal fistula developing during the RF atrial ablation. The most comprehensive technique involves a pre-operative procedure of developing a 3-D map of the operative field by CT scan or MRI displayed with real time 3-D electroanatomical maps to reveal the cardiac anatomical relationships. This mapping system may, or may not, be used with a contrast medium in the esophagus to better locate the position of the esophagus. The mapping systems allow the ablations to be precisely plotted on the atrium wall. The locations of some ablations may be changed or adjusted because of anatomical considerations. Contrast placement in the esophagus may be used independently of CT/MRI to allow real time visualization of the esophagus.
Thus, in some cases, the area of the atrium traversed by the esophagus is avoided during the ablation procedure to reduce or eliminate the risk of damaging the esophagus. In these cases, the success of the surgery may be compromised due to the skipped area of ablation.
Other methods utilized to reduce the risk of damage to the esophagus include reducing the electrical energy of the electrode in the vicinity of the esophagus. However, the adjustment is not significant and damage may still occur. In addition, the efficacy of the procedure may be compromised.
PRIOR ART FIG. 1, from Miller, illustrates a posterior view of the patient shown with the heart 11 in phantom lines lying in front of the esophagus 10. The esophagus is supported by the trachea 21 at one end and by the diaphragm 22 at the other end. Normal anatomical variation in the exact location of the atrium-esophageal relationship does occur. The right pulmonary vein 12 enters the atrium 13, and the desired pattern of optimal ablation lesions 14 are shown as they might appear in the mapping procedure. When viewing these proposed ablation lesions 14, either pre-operatively or intra-operatively, the surgeon may decide to change the location of some of the ablations because of the proximity to the esophagus 10. If a particular ablation(s) is considered necessary, regardless of the location of the esophagus, the RF power to the electrode may be reduced.
To manage the surgical field, to eliminate the possibility of an esophageal fistula, an esophageal catheter or tube 15 is inserted through the mouth or nose into the esophagus 10 and through the length of the esophagus past the diaphragm 22, as shown in PRIOR ART FIG. 2. The catheter 15 may include a radiologic marker or markers 16 to improve visualization of the location of the catheter 15 and esophagus 10.
To move the esophagus laterally in the surgical field, and to fix the displaced portion of the esophagus beyond the area of thermal lesions, a control wire 17 is inserted through the lumen of the catheter 15. As shown in PRIOR ART FIGS. 4 and 5, the control wires have a preformed curved intermediate portion 18, 20. As the curved portion moves through the catheter, the catheter is displaced along its longitudinal axis to follow the curve of the control wire. The control wire may be round, flattened, single strand or multi-strand, such as a guide wire. The control wire 17 is manipulated within the catheter to place the curved portion 18 near the atrium and to rotate the control wire to displace the catheter and esophagus away from the ablation lesions 14, laterally and posteriorly as the patient's anatomy permits, as shown in PRIOR ART FIG. 3. Depending on the relative size of the catheter lumen 27 and the control wire, a second control wire 19 having a similar curved portion 20 may be used. The control wires 17 and 19 may be used in conjunction with each other to produce one curve or, independently, to form the catheter in other shapes. The use of separate control wires allows the catheter to remain in place, once inserted, and to be bent in the area dictated by the anatomy of each individual patient. As shown in PRIOR ART FIG. 3, the curvature of the catheter is left lateral, however, the control wires may be manipulated to force the esophagus in the dorsal direction away from the heart or to the right laterally.
As shown in PRIOR ART FIGS. 6-8, the catheter 15 has control wires 17 and 19 attached to the sidewall at discrete points 26 along the catheter. By differential movement of the control wires and the catheter, respectively, as shown in PRIOR ART FIG. 8, the longitudinal shape of the catheter can be changed. In PRIOR ART FIG. 8, either the plunger 23 or the barrel 24 is moved relative to the other, thereby shortening one member in relation to the other and causing the catheter to bend in the mid-portion. In PRIOR ART FIG. 6, separate control wires 17 and 19 located in the sidewall of the catheter 15 can be moved to bend the catheter in different directions. In PRIOR ART FIG. 7 the control wire 25 is located in the lumen 27 and attached to the sidewall at 26. The catheter may be rotated in the esophagus to move the esophagus, as desired.
As we noted above, in relevant part, Miller requires use of a pair of control wires and/or a control wire utilizing a curved portion to manipulate the catheter to move the esophagus.
U.S. Pat. No. 5,170,803 to Hewson et al., incorporated by reference herein, describes a similar device that uses a looped wire provided as a hinge in order to manipulate the catheter for biasing the esophagus.
While these prior devices do manipulate associated catheters, their complexity raises issues with cost, reliability, reusability, etc. due to the force required to displace the catheter. Catheters having a high degree of flexibility are extremely difficult to insert into the human anatomy. Adding rigidity to the catheter for insertion severely hampers the ability of the wires to suitably displace the esophagus.
Thus, the invention provides a control wire for surgical procedures, which overcomes the disadvantages of the prior art control wires. The control wire of the present invention provides a control wire that can be utilized without a sheath to reduce the force needed to displace the anatomy as desired. The present control wire also provides easier manipulation and guidance to the user as to the direction of the manipulation.